Since the practice of commercial scale processes for the production of alkylpolyglycoside products is governed chiefly by economic factors, it is not economically feasible to produce a wide variety of alkylpolyglycoside products for distribution in commerce. This is unfortunate since the applications or end use of these compositions is highly dependent on combinations of factors including carbon chain length, degree of polymerization, and additional factors such as the co-presence of impurities or minor amounts of residual surfactants. A wide variety of applications of alkylpolyglycoside products is known in the prior art. Illustrations of such uses include hard surface cleaner compositions, U.S. Pat. Nos. 4,606,850, 4,627,931; polymerization aids, U.S. 4,657,999; liquid soaps and bubble baths, U.S. Pat. No. 4,668,422; carpet shampoo and cleaning uses, U.S. Pat. No. 4,678,595; corrosion inhibitors, U.S. Pat. No. 4,705,665; dishwashing detergents, U.S. Pat. No. 4,732,704; viscosity modifiers, U.S. Pat. No. 4,732,696; potentiating agents, U.S. Pat. No. 4,748,158; contact lens cleaning, U.S. 4,767,559; detergent and shampoos, U.S. Pat. Nos. 4,780,234, 4,565,647, 4,663,069, 4,483,779, 4,396,520, 4,599,188, 4,493,773, 4,536,319, 4,154,706, 4,304,679; and cosmetics, 4,323,468, 4,196,201. This list is not intended to be all inclusive but merely to illustrate the wide variety of applications and end uses of alkylpolyglycoside compositions requiring specialized formulation considerations, which for the most part must be determined empirically.
Donald E. Koeltzow and Allen D. Urfer, in a paper, "Preparation and Properties of Pure Alkyl Glucosides, Maltosides and Maltotriosides", JAOCS, Vol. 61, No. 10, pp. 1651-1655, October, 1984, examine various physical and functional properties of relatively pure alkyl glycosides having from 4 to 18 carbon atoms. This paper in turn refers to other publications dealing with synthesis of alkyl glucosides and an article by Francis A. Hughes and Baak W. Lew, reports on the physical and functional properties which render them suitable for use on biodegradable, surfactants, emulsifiers and detergents, "Physical and Functional Properties of Some Higher Alkyl Polyglucosides", JAOCS, Vol. 47, pp. 162-167, 1970.
U.S. Pat. No. 4,668,422, noted earlier, dealing with liquid soaps and bubble baths, prepared formulations in examples 6, 7 and 11 in which mixtures of two different alkylpolyglycosides were mixed in substantially equal amounts by weight, a C.sub.9-11 alkylpolyglycoside having a DP of 1.3 and a C.sub.12-13 alkylpolyglycoside having a DP of 2.8. At this substantially equal weight mixture no improvement is shown for examples 6, 7, or 11 over examples 1, 2, or 12 employing only one of the alkylpolyglycosides.
Similarly, in German Application DE 4 005 959, directed to liquid, foaming, cleaning agents, more specifically dishwashing detergents, an approach is taken whereby the mean degree of glycosidation (glycoside units per fatty alcohol residue) is not too high. The degree of glycosidation is controlled or determined by mixing two different alkylglycosides of differing alkyl lengths and differing degrees of glycosidation, in which each alkylpolyglycoside has an alkyl group of only one chain length, i.e. all C.sub.10 and all C.sub.11, or two different alkylpolyglycosides of mixed alkyl groups, i.e. C.sub.8-10 and C.sub.11-18, in which 1-10 parts of the C.sub.11-18 is mixed with 1 part of C.sub.8-10. Specifically shown are mixtures of C.sub.8 C.sub.10 G.sub.1.8 with a C.sub.12 C.sub.14 G.sub.1.2 or C.sub.12 C.sub.13 G.sub.1.1.
More recently, however, Japanese Patent Application No. 63-298821 filed 25 Nov. 1988 and laid open Jun. 5, 1990 (Kokai No. 145696/90) describes a higher alkylglycoside composition said to possess foaming characteristics equivalent to general purpose anionic surfactants, such as sodium dodecylbenzene sulfonate and sodium polyoxyethylene (3EO) dodecyl sulfate. The formulated compositions are described as a mixture of individual or pure higher alkylglycosides characterized in an essential component of at least 14% by weight of component (A) a decyl or/and (B) an undecyl polyglycoside with at least 14% by weight of component (C) a dodecyl or/and (D) a tridecyl polyglycoside in which (A) has an average degree of polymerization (DP) of 1.1 to about 4.1; (B) has an average DP of 1.4 to about 2.5; (C) has an average DP of 2.4 to about 3.8 and (D) has an average DP of 2.9 to about 4.6. Both the number of alkyl carbon atoms and the DP are described as (5) essential, particularly for component (A). Compositions are described comprising 28-92% by weight of (A) with the remainder being alkylglycosides having non-essential alkyl glycosides having alkyl groups of 11-14 and higher. Described are:
(1) mixtures of (A) with (i) n-hexadecylglycoside or (ii) n-tetradecylglycoside (as non-essential components); PA1 (2) a mixture of (A) with a dodecylglycloside having a DP of 1.8, outside the DP range for component (C) above as a non-essential component; and PA1 (3) mixtures of one or two of essential components (A) through (D) above with one non-essential component (either an alkyl group other than 10-13 carbon atoms or a DP outside the range for the essential components).
While the approach of the Japanese reference to mix glycosides of individual, single, alkyl groups could allow simulation of foaming surfactant properties, unfortunately, the use of mixtures of alkylpolyglycosides derived from readily available binary mixtures of fatty alcohols as described above are not encompassed within the teachings of the Japanese reference. The mixtures of alkylpolyglycosides derived from mono or relatively pure cut alcohols suggest a completely different approach than the unique, surprising and economically practicable approach hereinafter described with reference to the present invention.
In another approach, European Patent Application, EP 92355, published Oct. 26, 1983, describes the preparation of fatty glycoside mixtures by reaction of a saccharide-containing composition of the formula A--O--(G).sub.x, where A is hydrogen or an organo group of less than 8 carbon atoms, G is a saccharide and x is an integer of at least 1, with a lipophilic alcohol having at least 8 carbon atoms and a surfactant additive of the formula R.sub.f O(G).sub.n, where R.sub.f is a lipophilic organo group having at least 8 carbon atoms, G is a saccharide unit and n is an integer of at least 1. The reaction may be controlled to promote fatty glycoside mixtures of varying degrees of glycosidation. The applicants indicate generally that the mixture may be fractionated into divergent fatty glycoside fractions of differing HLB values, which may be recombined to make a fatty glycoside mixture of predetermined HLB values. No specific example of such a mixture is given. This approach, using individual divergent fractions, is similar to the Japanese approach of combining glycosides of individual, single, alkyl groups.
While these mixtures of monoglycosides and higher polyglycosides have properties permitting their function as detergents and surfactants, they have been typically formulated in the past with other anionic, nonionic or cationic surfactants to provide for enhanced surfactant properties, since standing alone they fell short of properties achieved by other surfactants, such as the ethoxylated surfactants.